Two Device ID’s on a RDM

I’ve been working on migration our current VMWare hosts to a new install that i’ve designed with optimised storage configuration and memory sharing as so to optimise the customer customer experience. While migrating VM’s from the last five hosts i’ve started running into issues with some VM’s that have RDMs attached. These RDMs won’t migrate to any of the new hosts, but they will migrate to the remaining old ones.

Usually this would mean that either the datastore containing the VMDK or the RDM pointer is not present on the new hosts or the RDM itself is presented to the new hosts. But i verified this and all those are available.

However on further investigation on the RDM i noticed that the RDM had two device ID’s, which is rather unusual.

Also when i did a storage refresh i received a lot of unexpected errors

First off i found that Device ID 214 was visible on the vSphere host. but Device ID 169 was not.

I’ve had a nice talk with VMWare support about this and their conclusion, somewhere in the storage controller the LUN is published to the vSphere hosts twice, causing the LUN to be found two times. However, it seems that the lower Device ID is somehow hidden when the higher Device ID is found, causing the VM to be locked on hosts that know about both ID’s.